1. Field of the Invention
The present invention relates to a fluid quality monitor and more specifically to a device and method using a photosensitive material for monitoring the quality of and amount of contamination within a fluid or lubricant.
2. Discussion of the Related Art
This invention relates to fluid monitoring devices and method, which are generally used in monitoring of lubricants, fuel, sewage, and the like. More particularly, the present invention projects a light emission through the subject fluid towards a photosensitive material. The photosensitive material detects the amount of light that is passed through the subject fluid. The apparatus then utilizes this information to interpret the quality of the fluid.
Fluid disposed within a system is normally monitored via a pressure sensor and a temperature sensor. The fluids are subjected to a filtration system to remove any impurities within the fluid. A pressure monitoring system can inform the operator if the filter is becoming obstructed.
Dielectric constant is measured using a capacitance sensor.
The viscosity can be measured using either a rheometer or a viscometer.
Particle count can be measured via any number of ways, such as providing a sonic or ultrasonic frequency between two frequency probes, which monitor the normal pulse to detect any deviation of that pulse. The deviation can be used to calculate the quantity or volume of contaminating particulate matter.
Wear metals are monitored via a variety of sensors. One such sensor is a ferrous sensor using electromagnets. This process is normally provided external to the normal lubricant fluid flow environment or closed loop system.
Water entrapment can be monitored via an impedance measurement or capacitance measurement of the dielectric constant.
The total base number (TBN) can be monitored. The TBN is a measure of a lubricant's reserve alkalinity. It is measured in milligrams of potassium hydroxide per gram (mg KOH/g). The TBN determines how effective the control of acids formed will be during the combustion process. The higher the TBN, the more effective it is in suspending wear-causing contaminants and reducing the corrosive effects of acids over an extended period of time.
The associated measurement ASTM D2896 and ASTM D4739-06 generally range from 6-80 mg KOH/g in modern lubricants, 7-10 mg for general automotive use and 10-15 for Diesel operations.
Marine grade lubricants generally will run from 15-50 mgKOH/g, but can be as high as 70 or 80 mg KOH/g as is the case of Exxon's MobileGuard 570 or respectively Castrol's Cyltech 80AW this high level is designed to allow a longer operating period between changes, under harsh operating conditions. When the TBN is measured at 2 mg KOH/g or less the lubricant is considered inadequate for engine protection, and is at risk for allowing corrosion to take place. Higher sulfur fuel will decrease the TBN faster due to the increased formation of sulfuric acid.
The TBN is normally measured off line, reducing the ability to identify a critical level that would need servicing.
Planar laser-induced fluorescence (PLIF) is an optical diagnostic technique widely used for flow visualization and quantitative measurements. PLIF has been shown to be used for velocity, concentration, temperature and pressure measurements. A typical PLIF setup consists a source of light (usually a laser), an arrangement of lenses to form a sheet, fluorescent medium, collection optics and a detector. The light from the source illuminates the medium, which then fluoresces.
This signal is captured by the detector and can be related to the various properties of the medium.
The typical lasers used as light sources are pulsed, which provide a higher peak power than the continuous-wave lasers. Also the short pulse time is useful for good temporal resolution. Some of the widely used laser sources are Nd:YAG laser, dye lasers, excimer lasers, and ion lasers. The light from the laser (usually a beam) is passed through a set of lenses and/or mirrors to form a sheet, which is then used to illuminate the medium. This medium is either made up of fluorescent material or can be seeded with a fluorescent substance. The signal is usually captured by a CCD or CMOS camera (sometimes intensified cameras are also used). Timing electronics is often used to synchronize pulsed light sources with intensified cameras.
In optics, a collimator may consist of a curved mirror or lens with some type of light source and/or an image at its focus. Collimators may be used with laser diodes and CO2 cutting lasers. Proper collimation of a laser source with long enough coherence length can be verified with a shearing interferometer.
Fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. This is achieved by adding a periodic variation to the refractive index of the fiber core, which generates a wavelength specific dielectric mirror. A fiber Bragg grating can therefore be used as an inline optical filter to block certain wavelengths, or as a wavelength-specific reflector.
Etched gratings such as those taught by U.S. Pat. No. 6,522,795 teach etching grooves or recessions (gratings) in an upper surface of a material to provide a controllable refractive index. The grating can be provided via a first and second cladding. If the index of the second cladding is different from that of the first cladding, the configuration of the first cladding provides an optical grating. If, however, the controllable index of the second cladding is adjusted to equal that of the first cladding, the grating becomes essentially transparent. This grating is particularly useful as a reconfigurable add/drop filter in a WDM optical communication system. It is also useful in grating-assisted couplers and variable optical delay lines.
Thus, what is desired is a fluid quality monitoring system that monitors the amount of contamination as well as any degradation.